1. Field of the Invention
The present invention relates to a method and device for controlling an internal combustion engine.
2. Description of the Related Art
Particularly in vehicles with start/stop technology, that is, when the engine is frequently switched off and switched on again during normal driving, a comfortable rundown of the internal combustion engine and a rapid restarting of the internal combustion engine are of great importance.
Published Japanese patent application document JP-2008298031 A describes a method in which the throttle valve of the internal combustion engine is closed in the rundown in order to suppress vibrations. That measure reduces the air charge in the cylinders in the internal combustion engine and hence reduces the roughness of the rundown, since compression and decompression are minimized.
For restarting of the internal combustion engine, however, as much air as possible is needed in the cylinders in which ignition takes place for the restart. There is therefore a conflict of objectives between a rapid engine start (which requires a lot of air in the cylinder) and a comfortable, that is, low-vibration, engine rundown (which requires little air in the cylinder). That conflict of objectives is resolved with the present invention.
Devices that alter the lift curve of, in particular, the intake valves of an internal combustion engine and thus regulate the air charge of the cylinders are generally known in the related art. In particular, it is known that the lift curve may be given any desired form over a wide range by electrohydraulic actuators. Internal combustion engines having such electrohydraulic variable valve timing do not require a throttle valve. It is also known that the lift curve of, in particular, the intake valves may be varied by adjustment of the camshaft. Such devices and the throttle valve with which the air charge of the cylinders may be altered are also referred to hereinafter as air-metering devices.